TIP: trying to deselect your local changes independently of the items affected by the pending merge can be difficult, and will sometimes NOT work if xlinks are involved. If you enable "Show changes grouped by changelists" in the Pending Changes Options, the client will automatically group items from each pending merge/cherrypick, and keep them separate from your local changes.

Of course, if your merge actually MERGED contributions from both source and destination, you'll have a problem...